1. Field of the Invention
The present invention relates to a method, system, and article of manufacture for generating a challenge response image including a recognizable image.
2. Description of the Related Art
A “CAPTCHA” (completely automated public Turing test) is a challenge-response test used to determine whether the responder to the CAPTCHA test is human, i.e., a test of the humanness of the receiver as opposed to a machine, such as an automated process or “bot”. This determination may be made in the context of determining whether to grant access to a resource guarded by the CAPTCHA to limit access to human users. Although the CAPTCHA challenge can be performed with respect to a remote person, the process typically involves a remote machine automatically asking a computer user or test recipient to complete a simple test, such as recognizing an alpha-numeric string presented on the recipient's computer screen. Typically that string is heavily distorted in such a way as to make machine recognition very difficult but recognition by a human is relatively easy.
The presumption is that because of the difficulty a computer process would have determining the string included in the image, a computer process is unlikely to solve the CAPTCHA, so that the recipient entering the correct solution is presumed to be human. CAPTCHAs can be deployed to protect systems vulnerable to e-mail spam, such as commercial webmail services, to stop automated posting to blogs, forums and wikis, whether as a result of commercial or political promotion, harassment and/or vandalism, to ensure that the user accessing information or a computer program is human, etc. CAPTCHAs may also be used to ensure that a response to an Internet poll is from a human to prevent the use of automated processes, referred to as “bots”, from manipulating the results.
Recently CAPTCHAs have been hacked, allowing automated processes to present the correct answer in response to the CAPTCHA image to present themselves as a human recipient, and in some cases gain access to the resource guarded by the CAPTCHA challenge-response test. For instance, many web sites reuse a set of CAPTCHA images. A hacker trying to use automated processes to get around the CAPTCHA may maintain a library of CAPTCHA images, such that when a CAPTCHA image is detected, the automated process or bot looks up the CAPTCHA image in the library to determine the response to return to the CAPTCHA challenge.